Numerous attempts were made prior to 1955 to convert various forms of carbon, including graphite, into its diamond form or other ultra-hard carbonaceous forms. None of these attempts have been adequately substantiated. A valid diamond synthesis was reported in 1955 but details were not revealed until 1959 (Nature 184:1094-8, 1959). At temperatures of 1200.degree. to 2400.degree. C. and pressures ranging from 55,000 to 100,000 atmospheres or more, carbon is converted into its diamond form in the presence of transition metals (chromium, manganese, iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum) or tantalum. Higher pressures are required at higher temperatures.
Rather esoteric means were also investigated in the guest for a more convenient graphite to diamond conversion. As reported in Phys. Rev. Letters 7:367 (1961), it was taught that diamond might be obtained in less than a microsecond by the action of extremely high pressure explosive shock waves on graphite. In fact, diamonds were actually recovered from carbon subjected to an explosive shock.
Epitaxial methods have also been reported where the decomposition of gases, such as methane, ethane and propane in contact with diamond powder was found to promote diamond growth. However, in performing epitaxial techniques, temperatures in the vicinity of 1300.degree. K. and pressures on the order of 10.sup.-3 to 10.sup.-4 atmospheres were found to be required.
It is obvious that the prior techniques employed in the fabrication of synthetic diamonds and other ultra-hard cabonaceous materials are at best cumbersome and expensive to carry out. The maintenance of any extremes in temperature and pressure requires enormous energy and sophisticated equipment, which in turn detracts from the widespread commercialization of synthetic diamond fabrication.